HR: 0800h
AN: T41B-1300    [Abstracts]
TI: GPS Velocity Field and Tectonics from the Ryukyu Arc to Taiwan
AU: * Segawa, K
EM: segawa@rcep.dpri.kyoto-u.ac.jp
AF: Disaster Prevention Resarch Institute,Kyoto University, Gokasho, Uji City,Kyoto, 611-0011 Japan
AU: Hashimoto, M
EM: hasimoto@rcep.dpri.kyoto-u.ac.jp
AF: Disaster Prevention Resarch Institute,Kyoto University, Gokasho, Uji City,Kyoto, 611-0011 Japan
AU: Kobayashi, T
EM: tkoba@rcep.dpri.kyoto-u.ac.jp
AF: Disaster Prevention Resarch Institute,Kyoto University, Gokasho, Uji City,Kyoto, 611-0011 Japan
AB: Convergence between the Philippine Sea and Eurasian plates is complicated around Taiwan. The Philippine Sea plate is subducting beneath the Eurasian plate on the Ryukyu trench side, while the Eurasian plate is subducting beneath the Philippine Sea plate on the Manila trench side. Furthermore, the Ryukyu islands and the northern part of Taiwan move toward the southeast, but the southern part of Taiwan moves toward the northwest. In this study, we try to model the plate kinematics of such a complicated convergence zone from the Ryukyu arc to the Taiwan using the GPS velocity field. We adopt the model of Matsu'ura et al.(1986) and Hashimoto and Jackson (1993) in which crustal deformation is represented as rigid block motions and deformation due to slip deficits along the fault of block boundary. In this study, we use the GPS data of the Ryukyu Arc from 30 stations of GEONET, operated by the Geographical Survey Institute, that provide good measurements of the crustal deformation. We estimate the secular velocities of GEONET stations. We also use the GPS data from 140 stations in Taiwan (Yu et al., 1997). All GPS velocities are converted to those relative to the Shanghai station of the International GPS Service (IGS). We assume 6 blocks and 22 faults based on the distribution of active faults and large earthquakes. Thus, we estimate the block motions and slip rate of faults. The model predicts that the Philippine Sea block moves northwest ward at about 75mm/yr relative to the Eurasian block. The south Ryukyu block and the south Taiwan block move in the southeast direction at about 28mm/yr and in the west-northwest direction at about 44mm/yr, respectively relative to the Eurasian block. The calculated velocities which are predicted by the model match the observation in the Ryukyu Arc and north of Philippine Sea block well. However, the calculated velocities in the west and south Taiwan blocks tend to have more northerly and southerly directions, respectively, than the observation. We estimate a slip deficit rate of about 78mm/yr between the Ryukyu Arc and Taiwan, and an estimated slip deficit rate is 95mm/yr between north and south Taiwan. These large slip deficit rates indicate that strain accumulation due to relative block motion is fast in these areas.
DE: 8104 Continental margins: convergent
DE: 8110 Continental tectonics: general (0905)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005